An off-duty Baltimore police officer, described as a 20-year veteran with tactical training, has barricaded himself at a house with a toddler after allegedly shooting a woman, who is now at a local hospital in serious condition.

The suspect, identified by police as James Smith, is holed up at a home on the West side of the city. SWAT members arrived at the scene several hours ago, and had removed a woman from the scene before paramedics arrived. Her clothing was seen to be covered in blood.

SWAT members then returned to the barricaded site. At 6:40 pm Eastern Time Baltimore police tweeted that negotiators were working to try and peacefully resolve the situation.

Baltimore Police Commissioner Anthony Batts has told reporters that the main concern at the moment is for the child still believed to be inside the home with Smith.

"The concern I have right now is slowing this scene down and making sure we get the child out safely," Batts said.